Obesity remains with us as a major health problem, and there is no reason to believe that the genetic, cultural, and environmental problems associated with the development of obesity are disappearing. Thus, the study of the physiological consequences of obesity is important. There are many facets of the obesity problem including: causes for the development of obesity, the consequences of becoming obese at an early age, the reasons for sustaining the obese state, the consequences of continuing obesity including development of metabolic or other chronic disease, and the modifications in physiological reactions to stress induced by obesity. Whereas considerable investigative effort has been devoted to study of weight reduction in the obese together with the associated metabolic and medical problems, less attention has been paid to the physiological responses of the obese to environmental variables such as: heat, cold, physical work, hypoxia, hyperoxia, hypo and hypercapnia, air pollutants, etc. The physiological consequences of being obese have only been partially identified. We would like to know what these consequences are, particularly if they are advantageous or adverse.